The present invention is concerned with photographic printing systems. In particular, the present invention is an improved neghold system for photographic printers which do not have automatic film advance mechanisms.
Photographic printers produce color or black and white prints from photographic film originals (generally negatives). High intensity light is passed through the photographic film and imaged on a photosensitive medium (generally photographic print paper). The photographic emulsion layers on the photosensitive medium are exposed and subsequently processed to produce a print (or transparency) of the scene contained in the photographic film original.
Photographic processing centers typically process film from many customers. General purpose printers are often used in these processing centers in order to produce color or black and white prints from a wide range of negative sizes which may include, for example, 110, 120, 126, 70mm, and 21/4 by 23/4 inch negative sizes. The desired prints may have 10 or more different sizes and may be either with or without borders. In addition, each negative may have two possible orientations during printing (i.e. the film may move from left to right, or from front to back through the printer).
One critical component of a general purpose printer is the neghold assembly, which holds the photographic film at the print gate where high intensity light is passed through the film and imaged onto the photosensitive medium. The neghold assembly must hold the film securely and must maintain the optical alignment of the film with respect to the remainder of the printer.
In many general purpose photographic printers, the photographic film is fed manually to the print gate. The film may be in the form of a long strip of material made from shorter strips which are spliced together for processing, or may be in short strips of approximately four frames each. This latter situation is generally the case when prints are being reordered by the customer. In either case, ease of positioning of the film in the neghold is very important.
Finally, because the large number of film sizes must be accomodated, and because each film size has two possible printing orientation, the neghold for each film size and orientation must be relatively low cost. This requirement has often led to significant compromises in the reliability of film holders and in the ease of positioning film within the neghold. Improvements in neghold assemblies used in general purpose printers are needed.